I audited 12 startup stacks in 90 days. Here is what breaks before 1,000 users every single time.

The thing that breaks before 1,000 users is almost never the code. Not a race condition. Not a memory leak. Not a missing index. Founders assume their app will collapse because of a bug they could have caught in PR review. Engineers assume they'll get paged for a logic error at 2am. Neither is true. In twelve startup audits, the first failure was always an infrastructure primitive. A limit someone didn't know existed. An environment that didn't exist at all. A default that worked perfectly at 50 users and silently died at 500. The first thing I check on any stack is the Supabase project plan. If it is on the free tier with more than 20 active users, the connection pool is already at 60% capacity. Most founders have no idea. They only find out when PGRST 104 appears in their logs at 3pm on a Tuesday — right when their biggest customer is running a demo. That error message means "too many clients already." Not "your query is slow." Not "your code is wrong." Just: you hit a number you did